In order to diagnose and treat the condition known as keratoconjunctivitis sicca (KCS), commonly known as "dry eye", it is useful to determine the osmolarity of the tears in the affected eye. It has been postulated that the condition of the eye is caused by a higher level of osmolarity in the tear fluid covering the eye than is generally desirable. In order to determine the level of the tear osmolarity, it is necessary to take samples of the tear from the eye itself. The volume of tear abstracted must be sufficient to carry out osmolarity measures by means which are well known in the art. On the other hand, the volume of liquid abstracted from the eye and the method of abstracting same must be such as to not stimulate the tear glands into provision of extra amounts of liquid at the moment of or during the sampling steps, which can lead to false readings.
Several approaches to this problem have been attempted and discussed by Applicant herein and co-workers in Arch Ophthalmol 96, 677, (1978). The samples in certain of these prior methods were so large as to raise serious questions of stimulation of the tear gland.
Mishima et al (Ophthalmology, Proceedings of the XXI International Congress, Mexico, DF, Mar. 8-14 1970; Amsterdam, Excerpta Medica, 1971, pt 2, pp 1801-1805) disclose and discuss a method wherein samples as small as 0.1 through 0.15 .mu.l are abstracted. This volume of sample is sufficiently small as to cause no problems of additional tear stimulation; however, the method suffers from certain practical problems.
In the method of Mishima there is utilized a small, straight pipette. A certain small quantity of oil is aspirated into the pipette, the tear sample is then abstracted and more oil is aspirated into the pipette to seal off the aspirated sample. Due to the very small size of the pipette utilized, practical difficulties have been encountered with the technique which may be due to the alteration of surface tension characteristics of the pipette by the oil which is aspirated in the first step. Further, since the technique of Mishima depends upon actual aspiration, problems relating to aspiration of air, contacting the eye, eliciting reflex tearing, and accidentally pulling out the tear strip of the sampled eye have been noted.
It was therefore believed desirable to develop an apparatus and method of utilizing same which maintains the highly desirable small volume requirements of Mishima without the practical problems which utilizing the technique brought about.